Liquid plastic and the method of applying a plastic coating



Patented F b. 21, 1939 I 2,148,381

UNITED STATES PATENT OFFICE LIQUID PLASTIC AND THE METHOD OF APPLYING A PLASTIC COATING Lester V. Slauter, Highland Park, and Harry Salter, Detroit, Micln, assignors to Michigan Cellulose Corporation, Detroit, Mich., a corporation of Michigan No Drawing. Application February 27, 1936, Serial No. 66,054

3 claims. (01. 134-79) This invention relates to improvements in celluand elasticity of the resultant coating on the artilose derivative plastic material coatings utilizing cle may be controlled; to provide a plastic material nitrocellulose, cellulose aceate, or a combination that while in a liquid state can be applied to an of both, and the method of applying a plastic maarticle and dried or cured in normal room tem- 5 13 coating to an c perature and humidity environment without spe- 5 The principal object of this invention is to procial-atmospheric conditioning process; and to provide a liquid plastic material, utilizing nitrocelluvide a novel and economical method of applying lose and/or cellulose acetate, be pp o an a plastic coating to an article, all of which are article, to form an enclosing protective and decoattained by our invention.

rative envelope. It is known that a heavy plastic coating may 10 A main je t is t provid a new m d wh he applied to an article by extruding the plastic by Single application a plastic coating material over the article to encase it; or the mastantlal thickness is applied to the article. terial may be moulded around the article; or the Another object is to provide a viscous plastic more common th d of applying multiple thin 15 solution, the ingredients of which remain in suscoatings to build up a coating of required t 16 pension indefinitely, thatcan be applied to an Hess may be used These methods.are not only article while in a liquid state. cost] y but they require much time and skill, to A furtherobject is to provide a plastic material gather with elaborate and costly operating equip coating for an article, utilizing nitrocellulose ment, n of which t n t i it their commercial 20 and/or cellulose acetate, in a liquid state to form application 2 coatmg of Substantial thickness Some of the known materials used in attemptother qbjects are: to provide plastic mate ing to obtain a thick or heavy coating to envelop rial utiliz ng nitrocellulose and/or cellulose acean article from a viscbusanitrocenulqse l tion, tate with suitable solvents to form a liquid solunecessitate controlled tempemgure and humidity tion; to provide in a plastic material certain ingrea d fectivel coated articles would dlents that will permit coating of uniform and S :535:23? T he majorit; of such defects being:

substantial thickness to be applied to an article having irregular convolutions; to provide in such That upon the rapld evaporation of the solvent a a plastic coating certain characteristics whereby refpgeyatmg effect is produced causingdia it will not while drying shrink to the extent that cipltatlon of moisture from the surroun ng a it will pull away and separate fromv the coated mosphere to collect on the newly coated surface article at the bottom of depressions, or tend to ret m rough streaked, and discolored duce. the coating thickness at the top of projeccoatmg; or due the Surroundmg atmosphere t on the article; to provide in a plastic mate the solvents of the immediate exterior of the newly rial utilizing nitrocellulose and/or cellulose acetate coated surface evaporate leavmg an impenetrable 5 certain characteristics whereby the shrinkage of surface mm and the Solvent P is trapped th m t ri l while drying may be controlled; to neath this surface film vaporlzes or boils, formprovid in such a plastic material certain ingan unshapely wrinkled orblistered effect upon gredients whereby the material may be applied t surface of the coating- It has been found in a liquid state, and upon drying obtain physical that When using Controlled pe ture a d characteristics superior to those of the heretofore humidity, if the Object bemg coated P05565885 a known molded, formed or extruded plastic cellu- Surface of fine detail such asfingmvlng lose nitrate or plastic cellulose acetate; to pros ins, he coating w applied r m a vis us vide a liquid plastic material incorporating nitro- Solu w D5 drying; Stretch y from the cellulose and/or cellulose acetate dissolved in depressions, thus a1m0$t obliterating the details 45 suitable solvents, that will permit its application of the design. In an attempt to overcome these to the article and drying in a normal room defects, various curing and drying processes have temperature and humidity, therefore, being par-. been tried, but heretofore none have proven enticula'rly adapted for economical commercial tirely successfuli Such objectionable features, as

use, the resultantcoatingof the finished article above enumerated, are avoided by our invention. 50 having superior physical properties and an en- We have found that, by treating the nitrohanced appearance over those of other known cellulose, cellulose acetate, or the plastic celluplastics; to provide in a plastic material incorpolose derivative, with a solution of combined s0l-, ratingnitrocelluloseand/or cellulose acetate, cervents, latent-solvents, and diluents in such a tain ingredients whereby the degree of hardness manner that the last solvent to vaporize isnonhygroscopic in character, we obtained a viscous liquid plastic solution that is commercially practical because temperature and/or humidity control are not necessary in curing or drying the liquid plastic coating.

Further, that by treating the nitrocellulose, cellulose acetate, or the plastic cellulose derivative with a solution of combined solvents as: (l) a solvent of low boiling point, such as an aliphatic ketone or an aliphatic ester to act as a vehicle solvent, (2) a solvent, such as an aliphatic alcohol of low boiling point, but higher than the aforementioned solvent to act as a' latent solvent as solvent (1) evaporates, and (3) a non-hygroscopic hydrocarbon solvent, such as a non-hygroscopic hydrocarbon with a medium boiling point, higher than the preceding solvents, the resulting liquid plastic does not require a curing or drying process, after it has been applied to the article.

Still further we have found that, the nonhygroscopic hydrocarbon solvent (3) with a medium boiling point, but a higher boiling point than the preceding latent solvent, will act first, as a diluent, second, because of its non-hygroscopic nature, willrender the condensed moisture on the coating surface ineffective, and third, as a jelling agent when the vehicle solvent and the latent solvent have evaporated. We have thus obtained a liquid plastic in the state of a viscous solution that attains the objects relative to the material hereinbefore enumerated.

More specifically, We have found that, by treating a quantity of one-half to three and onehalf pounds of nitrocellulose, cellulose acetate, or the plastic 'cellulose derivative with a solution of combined solvents comprising (1) 50 to 90% acetone, ethyl methyl ketone, or ethyl acetate, (2) 5 to 25% ethyl alcohol, propyl alcohol, iso-propyl alcohol, butyl alcohol, or iso-butyl alcohol, and (3) 5 to 25% benzene, toluene, xylene, saturated naptha, or unsaturated naptha, to form a gallon of solution, the resultant liquid plastic in the state of a viscous solution, when applied to an article produces a heavy coating, the thickness of which can be varied as desired and does not require a curing or drying process after its application to the article.

The viscosity of the liquid plastic, for the purpose herein later described, may be varied by altering the above mentioned proportion of solids and solvents.

The ingredients of the solution, also the quan-- tity of each ingredient, to attain various drying characteristics, may be combined as desired within the range and percentages above mentioned.

By Way of example, but not of limitation, the following formula of a liquid plastic material successfully used, is given:

1 pounds plastic cellulose derivative, such as pyroxylin, dissolved in solvents in the proportion 1 of 80% acetone; 10% iso-propyl alcohol, and 10% toluene, to form one gallon of solution.

As will be seen from the foregoing specific example, acetone, which is used as the vehiclesolvent hereinbefore described under (1), is a solvent of low boiling point, namely, 56.5? C. The iso-propyl alcohol which acts as a latent solvent as described under (2) during the time solvent (1) evaporates, has a boiling point of 823 C., and the toluene, which forms the non-hygroscopic (3) with a medium boiling point, has a boiling point of 1l0.8 C. The boiling points above given are known specific properties of the solvents named, as can be readily established by reference to any standard reference book.

From the nature of the solvents herein enumerated it is obvious that additional agents such as plasticizers, drying oils, gums, and natural or synthetic resins may be added to vary the characteristics of the liquid plastic, and it is our intention that the addition of such agents which are miscible with the ingredients above enumerated is not to be construed as a departure from the spirit and scope of our invention.

The liquid plastic above described may be applied to metallic or wooden articles, glass, rubber, leather, compounded substances, paper, fabric, or similar articles by immersing the article in the liquid plastic solution of predetermined viscosity and then withdrawing the said article from the solution and allowing it to dry in a normal room temperature and atmosphere.

When the plastic material has been prepared as above described with solvents having the characteristics set forth the vehicle solvent (1) which in the specific example is acetone, will evaporate quite rapidly at ordinary room temperature without necessitating the use of any baking or forced drying step. During the evaporation of the acetone, solvent (2) iso-propyl alcohol and solvent (3) toluene remain'relatively latent. The more rapid evaporation of the acetone results in forming what may be termed a confining film on both the inner and outer surface of the coating, while the non-evaporation or the relatively slight degree of evaporation of the iso-propyl alcohol and toluene tend to keep the plastic material confined between the inner and outer films in a jelled condition. As the toluene solvent (3) is non-hygroscopic it will in addition to acting as a jelling agent during the evaporation of solvent (1) (acetone) render any condensed moisture on the coating surface ineffective. This is due to the fact that as the solvents employed are of low boiling points the evaporation takes place quite rapidly and by the time the cooling or refrigerating effect of the evaporation has proceeded to a point such as would ordinarily cause precipitation of atmospheric moisture upon the article to be coated, the evaporation has proceeded down to the toluene content which, because of its nonhygroscopic properties, prevents marks appearmg on the finished surface, which would otherwise be caused by such condensation. Therefore it has been found in actual practice with the present invention unnecessary to resort to such steps as have heretofore been thought necessary, such as carefully controlled temperature and humidity. As will also be seen when the solvents are carefully selected in accordance with the foregoing disclosure so that all are of low boiling points but selected so that the main vehicle solvent (1) the latent solvent (2), and the nonhygroscopic solvent (3) evaporate in succession in the order given, unexpected and desirable results are obtainable in commercial practice. The formation of the confining films on the outer and inner surfaces between which the remaining solvent is confined in a jelled condition enables the adherent coating to flow between the confining films and automatically adjust itself to the exact contour of the article coated thereby to insure a relatively uniform thickness of coating.

7 The thickness of the coating, which is relasion or application is controlled by the viscosity of the liquid plastic solution and/or by the rate of speed at which the article is withdrawn from the solution.

The coating is maintained of uniform thickness by maintaining a uniform rate of speed while withdrawing the article from the solution, or the thickness of the coating'may be varied by varying the rate of speed while withdrawing the article.

Thus a coating of gradually tapering thickness,

and/or varying translucency, or a coating of intermittently varying thickness and/or translucency may be applied to the article.

We claim: I

1. A plastic material essentially comprising a plastic cellulose derivative dissolved in a solvent mixture consisting of acetone, iso-propyl alcohol and toluene, forming a viscous solution.

2. A plastic material essentially comprising a cellulose derivative dissolved in a solvent mixture consisting of acetone, iso-propyl alcohol, and toluene, forming a viscous solution, the acetone comprising approximately 80% of such solvent mixture, the iso-propyl alcohol approximately 10%, and the toluene approximately 10%.

, 3. A plastic material essentially comprising a cellulose derivative dissolved in a solvent mixture consisting of acetone, iso-propyl alcohol, and toluene, forming a viscous solution, the acetone comprising from 50% to 90% of such solvent mixture, the iso-propyl alcohol from 5% to 25% thereof, and the toluene from 5% to 25%.

' LESTER V. SLAUTER.

HARRY SAL'I'ER. 

